1. Field of the Invention
The present invention relates to an image capturing apparatus, playback apparatus, control method, image capturing system, and recording medium, and particularly to a technique for binocular stereopsis using images for right and left eyes obtained from light beams which have passed through different regions of an exit pupil of an imaging optical system.
2. Description of the Related Art
In recent years, playback apparatuses such as television receivers and mobile phones, each of which has a display device for stereoscopically displaying contents have prevailed. Contents for stereopsis to be displayed by such playback apparatus are not limited to those which are provided by specific providers of television broadcast programs, DVDs, and the like, and contents created by users can be used.
As one method of allowing an observer to perceive a solid, a binocular stereopsis method which allows the observer to perceive a binocular disparity by presenting different images for right and left eyes, which have an image nonalignment amount between them to the right and left eyes of the observer is known. Since most of the aforementioned stereoscopic display devices adopt the binocular stereopsis method, image capturing apparatuses which can capture still images or moving images for stereopsis, each of which includes images for right and left eyes, have also prevailed recently. For example, such image capturing apparatus which can capture images for binocular stereopsis has two imaging optical systems which are disposed to set a base-line length, and outputs images obtained from light beams which have passed through the respective imaging optical systems as those for binocular stereopsis.
On the other hand, when an observer views a content for stereopsis using a stereoscopic display device, a viewing distance (a distance between a display surface and eyeballs of the observer) recommended according to a physical size of a display region is set. This viewing distance is set according to an average horizontal eyesight of users. In most of contents for stereopsis, which are provided by the providers, as described above, an image nonalignment amount between images for right and left eyes of a content is adjusted so that the binocular disparity hardly gives a tired feeling to the observer when that content is viewed at the recommended viewing distance.
However, since a content for stereopsis created by a user may not consider any tired feeling of which the binocular disparity is to be given to an observer, some display devices have a function of adjusting an image nonalignment amount between images for right and left eyes. Japanese Patent No. 3978392 discloses a technique which adjusts a stereoscopic effect given to an observer by determining an image shift amount of images for right and left eyes based on: information of a base-line length of two imaging optical systems: and a distance to an intersection of optical axes of the two imaging optical systems, which are included in images for binocular stereopsis.
Some image capturing apparatuses can capture images for binocular stereopsis using only one imaging optical system in recent years. Japanese Patent No. 4027113 discloses an image capturing apparatus in which each pixel of an image capturing element has a plurality of light-receiving elements, as shown in FIG. 2, and the respective light-receiving elements photoelectrically convert light beams which have passed through different regions of an exit pupil of the imaging optical system, thus capturing images for binocular stereopsis.
However, the image capturing apparatus disclosed in Japanese Patent No. 4027113 does not consider any function of appropriately adjusting an image nonalignment amount between images for right and left eyes.